Frequency control means



Nov. 2, 1948.

R. H. RANGER FREQUENCY CONTROL MEANS 2 vsneaks-sheet 1 Filed June 10,1944 NOVa 2, 1948. K I R H RANGER LS FREQUENCY CONTROL MEANS Filed Junel0, .1944 2 Sheets-SheetB Patented Nov. 2, 1948 FREQUENCY CONTROL MEANSRichard H. Ranger, United States Army, Newark, N. J.

Application June 10, 1944, Serial No. 539,696

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment of anyroyalty thereon.

This invention relates to means for controlling the frequency ofelectricity supplied to radio apparatus including both transmitters andreceivers.

This frequency control is attained by providing a standard of reference,which may be adjusted by hand to give a selected standard outputfrequency, an oscillator simultaneously set to the same approximatefrequency, and a motor which responds to any deviation of the oscillatorfrom the selected standard frequency and causes the oscillator to beadjusted so that its output fren quency is made to correspond and remainon the frequency originally selected. In order to permit the selectionof any frequency within the range covered by the instrument, there isprovided a piezoelectric crystal, which affords a source of a series offrequencies by selection of harmonics of the fundamental frequency ofthe crystal, and an adjustable oscillator, which is adjustablesimultaneously with the selection of said harmonics and thus affords asource of a second series of frequencies having values which may differfrom those of said first series, and a second adjustable oscillatorhaving a lower and limited range of output frequencies and serving tosupply the values of frequencies intermediate those represented by anytwo harmonics of the first mentioned series of frequencies. A motor iselectrically connected into a circuit involving the output of thiscrystal and these oscillators so that the motor is movable in responseto any difference in frequency between the selected harmonic of saidcrystal and said oscillators, this motor having mechanical connectionswith means for adjusting the output frequency of the first oscillator tothe frequency of the selected harmonic plus or minus the frequency ofthe second oscillator.

It is an object of this invention to provide a device for controllingthe frequency of a radio apparatus. This device comprises a circuitcontaining a crystal arranged to oscillate and ccntrolled in such a waythat various harmonics may be selected, a master oscillator alsocontrolled in such a way that its output frequency may be selected, amixer circuit in which the selected harmonic and the selected frequencymay be mixed to produce a beat, a second oscillator which, too, may becontrolled -to afford selection of the frequency emitted thereby, .andto-which said beat is to be compared, an electric motor movable inv.response to vany difference in frequency between said beat and theoutput frequency of said second oscillator, and a mechanical connectionbetween said motor and the controller of said master oscillator, wherebysaid motor adjusts the frequency of said master oscillator to match thatof the selected harmonic plus or minus that of said reierenceoscillator. In other words, when a variation occurs in the frequency ofthe electricity enere gizing a radio apparatus, a motor is operatedwhich restores the frequency to that which was pre-selected.

Another object of this inventionis the provision ofk a pair of operatingdevices such that the frequency of the electricity which energizes aradio apparatus may be varied by relatively large or small differencesor increments.

Yet another object of this invention is to supply, in addition to themeans for selecting a desired harmonic of the oscillations afforded by acrystal, means operable in the reverse sense .to said selecting means,whereby the tuning of the harmonic selected is maintained constantdespite necessary adjustments of the main control to cover intermediatefrequencies.

Further objects and explanation of this invention are set forth in thespecification below and in the annexed drawings.

In the drawings:

Figure 1 is a block diagram.

Figure 2 is an electrical circuit diagram.

Figure 3 is a top or plan View of the operating mechanism.

Figure 4 is a vertical cross section on line d-ll of Figure 3.

But one modification of my device is to be described in thespecification and depicted in the accompanying drawings. Many othermodifications will readily appear to those skilled in this art.

The frequency control mechanism of this invention comprises a crystal Eelectrically connected to a harmonic amplier 6 which in turn iselectrically connected to a harmonic selector 'l having a selector orcontrol element 8 forming a part thereof. A master oscillator 9 isprovided with a tuning or selecting mechanism l and with an additionalselecting mechanism Il. Selector 1 and master oscillator 9 are bothelectrically connected to the mixer circuit l2 which, in turn, iselectrically connected to a beat-tuning circuit i3. A referenceoscillator I4 is provided and is electrically connected to aphase-shift-control circuit i5, which also receives the electricaloutput ofthe beat-tuning circuit i3. Circuit I5 includes, as ,a

- part thereof, a two-phase motor I6. The output of master oscillator 9is connected to the main transmitter I9. A double-pole double-throwmanually operable switch 26 is connected to the output side oftransmitter I9 and to the input side of receiver I8 and serves toconnect antenna 2| and ground 22 to transmitter I9 or t0 receiver` I8.Transmitter I9 has an antenna tuning circuit 24 electrically connectedthereto. Receiver I8 contains a manually adjustable tuning element 4lmovable by means of shaft 26 and a mechanically adjustable tuningelement 48 movable by means of a mechanical connection 49 connectingwith motor I6. Mechanical connections 45 and 49 each contain a clutch,5B and 5I, respectively. Clutches 50 and 5I are mechanicallyinterconnected by means of interlock 52 so that when one of theseclutches is engaged the other must be disengaged. A double-pole,single-throw switch 53 controls the circuit connections between masteroscillator 9 and mixer I2 and also between receiver I8 and mixer I2 insuch a way that one circuit is closed when the other is open. Amechanical connection 54 fastens interlock 52 to the operatingconnection 23 between switches 21) and 53.

The means for adjusting this mechanism are provided by a knob 25 turninga shaft which i-s indicated by dotted line 26 which operates harmonicselector circuit 1, master oscillator 9, antenna tuning 24 and receiverI8. This means also includes a ine adjustment knob 27 which turns ashaft 28 controlling reference oscillator Il, beat-tuning circuit I3,and tuning mechamsm or capacitor 29 of a harmonic trimmer 3B. Betweenshafts 26 and 2S there is provided a mechanical interlock generallyindicated at 3|. Interlock 3| has a mechanical ratio of 40 to 1 so thatknob 25 provides a main or coarse adjustment While knob 21 provides a neadjustment. In other words the main shaft 26 changes all the unitsconnected to it, first, by its main discrete steps and, second, by meansof gearing from the line shaft 28 to points in between the main discretesteps.

In order that the harmonic selected by Controller 8 may serve as a fixedreference and remain constant despite the intermediate adjustment ofshaft 26 caused by movement of the ne knob 21, means must be providedfor compensating for any changes in the adjustment of controller 8. Thisis done by means of harmonic trimmer circuit 30 and the tuning mechanism29 forming part of this trimmer circuit. Capacitor 29 is operated in theopposite direction or reverse sense to the controller 8 and therebyserves to keep the frequency of harmonic selector 'I constant as thefine knob turns with 29 directly and 8 indirectly by the mechanical link3|' between the shafts 28 and 26. The electric circuit shown in Figure 2aids in accomplishing this. This represents the harmonic selector 'Imade up of the main inductance 46 and the main capacitor 8. Capacitor 29is connected in series with capacitor B. Capacitor 8 varies in the ratio4 to 1 while capacitor 29 must be larger, a convenient size being fourtimes that of capacitor 8. That is to say, if-capacitor 8 has valueswhich are in the ratio of 4 to l, capacitor 29 should have values of 16to 4. It is still not possible to get absolute control of thissituation, so it may.

be necessary to add the series tuning element shown as fixed capacitor32 and inductance 33 which provide resonance at the lower end of theband worked with. The eiect of this series tuning element will be toincrease the effective capacity on the low end.

III

A more complete showing of the details of the manual control is to befound in Figures 3 and 4. There, it will be seen that main knob 25 has aplurality of hemi-spherical depressions 34 in its shaft which cooperate(one at a time) with a detent formed by ball 35 and spring 36. Knob 25carries gear 3l on it (see Figure 4). This gear serves as a sun gearabout which planet gears 35 may rotate. Planet gears 38 mesh -at theirouter portions with internal gear 39 forming part of a ring 46 mountedon the end of shaft 26. Planet gears 38 are rotatably mounted on pins Ilcarried by lever 42 which has at its outer end a segment 43 which mesheswith gear dll connected to knob 21 and shaft 28. The gear reductionratio between shaft 28 and 26 is 40 to l.

The operation of my device is as follows: A frequency is selected by themain adjustment 25. By shaft 26 this tunes master oscillator 9 andantenna tuning 24 for the same frequency. Also harmonic selector 'Ipicks a harmonic of crystal 5. This harmonic will differ from thefrequency of the master oscillator 9 so as to give a beat in the outputof the mixer I2. This beat will be compared with the frequency of thesecond ref- Vbeat is higher than the reference oscillator, the

phase shift controller I5 will cause two-phase motor I 6 to turn tobring the frequency of the beat into accord with the referenceoscillator I4, A convenient frequency for crystal 5 is 200 kilocycles(kc.) This crystal serves as a master reference. Assume a band coveragefrom 4 to 8 megacycles (me). This means twenty 200 kc. harmonic pointsfrom 4 to 8 me. As there is a spread of 200 kc. between any twoharmonics of the crystal 5 such as for example the twentysecond andtwenty-third at 4.4 mc. and 4.6 mc. respectively, reference oscillatorI4 must cover this range. It is convenient to accomplish this forexample in the normal intermediate frequency ranges as from 300 kc. to500 kc. This will give a frequency range well handled by the normal 4 tol capacitor in tuning the reference oscillator I4. At the same time thisis as low a frequency as is conveniently possible without getting intotrouble. The lower the frequency, the more accurate the finaladjustment. Now if the master oscillator setting is at 4.7 mc., and theharmonic selector is on the twenty-second harmonic or 4.4 mc., therewill be a beat of 0.3 mc. or 300 kc. in the mixer I2. If the fineadjustment knob 2'! is at zero, the shaft 28 will have turned thereference oscillator I4 to its lower end or 300 kc., and the set is inadjustment. If the master oscillator 9 is slightly below 47 mc., thebeat note will be less than 300 kc., and the phaseshift controller I5and its associated two-phase motor I6 will act mechanically to decreasetrimmer capacitor control Il to raise the frequency of the masteroscillator 9. Now, if the fine adjustment knob is turned up kc., thiswill act to increase reference oscillator I2 frequency to 400 kc. andbeat tuning I3 to 400 kc. and harmonic trimmer 30 to hold the harmonicselector I to the same twenty-second harmonic by decreasing thecapacitor 29. At the same time, the mechanical link 3| will turn themain shaft 26, to increase the frequency of the master oscillator 9 andantenna tuning 24 by this same 100 kc. If fine readjustment is necessaryto make the master oscillator 9 now exactly 100 kc. higher or 4.8 mc.,the phase controller I5 will again act through two-phase motor I6 ontrimmer II on the Vmaster oscillator 9.

Receiver I8 is a superheterodyne receiver and depends on the masteroscillator to act as the local oscillator. The intermediate frequency is200 kc. So when the shift is made from transmit to receive, the sameswitching which operates 2t will operate to move the detent mechanism 35and 36 around one notch in such a direction as to drop it back one stepso that the master oscillator and harmonic selector will drop back 200kc. The receiver, by the same token, will` be brought to its correcttuning point of say 4.8 mc. It is 200 kc. too high in tuning ontransmission.

When it is decided to operate transmitter I9 or receiver I8, switch ismanually set in the desired position so that it connects the antenna 2 Iand ground 22 to the transmitter I9 or tothe receiver IS. Detentyieldingly retains knob 25 in the position to which it is moved. Knob 25is manually adjusted, turning shaft 26, which moves controller 8 so asto select a harmonic of the out put frequency of crystal controlledoscillator 5. This ouput contains twenty available harmonics which arespaced 200 kc. apart. If it is desired to operate at a frequencyintermediate one of those provided by the harmonic selector 1, knob 2Iand shaft 28 are manually adjusted so that in effect the numerical valueof the setting of the reference oscillator I (having a range of 200 kc.)is added to the frequency of the harmonic selector. It would be equallypossible to work down from a selected harmonic to intermediate values inwhich case the value of the second reference oscillator would besubtracted from the main frequency setting. Whenever referenceoscillator I4 is adjusted, harmonic trimmer 30 is also adjusted in theopposite sense, so that the frequency output from harmonic selector 1,modified by the harmonic trimmer 3l), is fed to mixer circuit I2. Thefrequency output from master oscillator 9, as adjusted by controller I0,is also fed to mixer I2 and a beat between these two frequencies occurs.The lpurpose of the IF or beat tuning circuit I3 is to select the beatout of all the hash that may be present in the input from the masteroscillator 9 and from harmonic selector 'I so that a nice, clear beat isaccomplished. This beat is then combined with the frequency output of IFor reference oscillator IQ in a normal two-phase arrangement with 90shift of phase by means of phase-shift controller circuit I5. This typecircuit is shown in detail in my copending application Serial Number494,892, filed July 14, 1943, now abandoned, where two frequencies arecompared and a motor is made to run in one direction or the otherdepending upon whether one frequency is above or below the other.However, to accomplish the adjustment of the master oscillator frequencyto the proper value, any system for this purpose, already known to theart, which operates on a comparison of two frequencies may be usedinstead. If there is any frequency difference between the beat and theoutput of reference oscillator I4, two-phase motor I5 turns controllerIl by means of mechanical connection and adjusts the output of thismaster oscillator into agreement with the setting which has been made onthe reference oscillator I4.

The master oscillator 9 must be 300 kc. off the harmonic selected inorder to be in adjustment at the low end of the flne shaft setting. Atthis point the primary beat between master oscillator 9 and the selectedharmonic will be 300 kc. If it is not, there will be a beat between thisfrequency and the frequency put out by the reference oscillator I4 whichis at 300 kc. This secondary beatv actu ates the two-phase motor I6 andthis automatically adjustscontrol I I of the master oscillator 9 to thepoint where the oscillator is 300 kc. oi the selected harmonic. The beatbetween the output of the mixer I2 and reference oscillator I4 thusapproaches zero.

I claim:

l. Means for maintaining constant the frequency at which radio apparatusoperates, said means comprising, first means adapted to generate a rstselected frequency, second means adapted to generate av second selectedfrequency, a circuit arranged to receive said first frequency and saidsecond frequency and to transmit the beat between said frequencies, rstmanually operable means controlling the respective frequencies of thecomponent waves which together form said beat, third means adapted togenerate a third selected frequency, second manually operw abie meansinterlocked'with said first manually1 operable means and affording amore delicate control of the respective frequencies of the componentwaves which together form said beat, a two-phase motor operable inresponse to any frequency difference between said beat and said thirdfrequency, a mechanical connection between said motor and said secondmeans, whereby said motor tunes said second means so that said beatfrequency is equal to the frequency of said third frequency andtherefore the operating frequency ofthe apparatus is maintainedconstant, and sixth means mechanically connectedunder the control ofsaid second manually operable means and electrically connected to thefirst means so as to tune said first means to compensate for any changein the first selected frequency caused by operation of said firstmanually operable means.

2. Radio apparatus having high inherent frequency stability andcomprising a first source of electricity cf a few, relatively stablefrequencies, a second source of electricity o-f a, larger number ofrelatively unstable frequencies, means for mixing said frequencies from.said sources and for producing a beat frequency between them, a thirdsource of electricity adjustable to produce a lower order frequency, anelectric motor electrically connected to respond to any phase differencebetween said beat frequency and said lower order frequency selected, amechanism driven by said motor to cause said beat frequency to matchsaid lower order frequency selected, a mechanical coupling connectingsaid rst source and said second source to said third source and manuallyoperable to tune the output frequency of said sources to select desiredfrequencies, and a frequency-controlling element mounted for movem-entin response to movements of said coupling and interconnected in circuitwith said first source so as to vary the frequency of said first sourcein the opposite direction to the variation in its frequency under thecontrol of said coupling.

3. A controller for stabilizing the operational frequency of a radioapparatus, said controller being constituted by an electric circuitarranged to generate a relatively fixed frequency and con taining anadjustable element operable to select harmonics of said frequency, amaster oscillator arranged to generate a relatively Variable frequencyand adjustable to select the frequency generated, a mixer circuitVconnected to said electric circuit and to said master oscillator so asto receive the outputs thereof and combine said outputs into a beat, areference oscillator arranged to generate one of a band of relativelylow frequencies and adjustable to select the frequency of the wavegenerated, a phase shift circuit including a two-phase motor andconnected to said mixer circuit and to said reference oscillator so asto receive said beat and said frequency selected for said referenceIoscillator, said motor being operable in response to any differencetherebetween, a mechanical connection between said motor and said masteroscillator whereby the output frequency of said master oscillator is ad-.iusted by said motor to eliminate any frequency difference between saidbeat and the output frequency of said reference oscillator, and a secondadjustable element for selecting the frequency generated by thereference oscillator, said second adjustable element being mechanicallyinterlocked with the adjustable element of said electrical circuit andoperable upon said electric circuit to maintain substantially constantthe frequency of the harmonic selected for said electric circuit.

4. A frequency control system comprising: first oscillator meansincluding first tuning means for adjusting the output frequency of therst oscillator means to a selected one of at least two differentfrequencies; master oscillator means including second tuning means foradjusting the output frequency of such master oscillator means;reference oscillator means including third tuning means for adjustingthe output frequency of the reference oscillator means to a selectedvalue which is smaller than that of the diierence in frequency betweenany two adjacent frequencies of those frequencies from which thefrequency of the first oscillator means may be selected; mixer meansderiving input from the first oscillator means and the master oscillatormeans and producing a beat frequency having a value which is equal tothe diiference between the frequencies of the respective inputs;frequency-setting means derivingr input from the mixer means and fromthe reference oscillator means, such frequencysetting means beingconnected to the master oscillator means and responsive to a differencebetween the respective frequencies of its inputs to tune the masteroscillator means and thus to bring the output frequency of the masteroscillator means to a value such that the beat frequency output of themixer means equals the output frequency of the reference oscillatormeans; first selector means for operating the rst and second tuningmeans; second selector means for operating the third tuning means;interlocking means interlocking the second selector means to the rstselector means so that operation of the second selector means to anextent corresponding to a certain change of frequency causes operationof the first selector means to an extent corresponding to the samechange of frequency; and fourth tuning means operated by the secondselector means and connected to the rst oscillator means to maintain thefrequency of the first oscillator at the selected value corresponding tothe position of the first selector means.

5. A frequency control system, as described in claim 4, in which themixer means include beat tuning means for the purpose of selecting aclear beat out of the inputs to the mixer means.

6. A frequency control system, as described in claim 4, in which thefrequency-setting means include a two-phase motor connected to themaster oscillator means and include also means so connecting the motorwith the mixer means and the reference oscillator means that the motoris responsive to a difference between the respective frequencies of itsinputs to tune the master oscillator means.

RICHARD H. RANGER.

REFERENCES CITED The` following references are of record in the nie ofthis patent:

UNITED STATES PATENTS

